Chapter 13-16

Question 1

Mendel

Answer 1

The father of modern genetics, disapproved the blending theory with his work with garden pea plants. Provided the basis for what we know about inheritance today

Question 2

Dominance (Complete Dominance)

Answer 2

If you have to different alleles the one that is apparent is the dominant allele, represented by a capital letter

Question 3

Recessive Allele

Answer 3

If you have two different alleles the one that is hidden, is called the recessive allele and is represented by a lower case letter

Question 4

Homozygous

Answer 4

If an individual has both the same alleles (AA or aa)

Question 5

Heterozygous

Answer 5

If an individual has different alleles (Aa)

Question 6

Theory of Segregation

Answer 6

An individual inherits a unit of information (allele) about a trait from each parent. An individual passes on only one of their alleles to his offspring, and the other allele comes from the other parent. During gamete formation, the alleles segregate from each other

Question 7

Tracking Generation

Answer 7

Paternal generation mates to produce (P), first generation offspring mate to produce (F1), second generation offspring (F2)

Question 8

Mendels Monohybrid Cross Results

Answer 8

F2 plants showed dominant to recessive ratio that averaged 3:1

Question 9

Genotype

Answer 9

Combination of alleles that an individual has (Aa, aa, AA)

Question 10

Phenotype

Answer 10

The expressed trait that an individual has (Brown eyes, green eyes, blue eyes)

Question 11

Gene

Answer 11

A unit of DNA that codes for a specific trait, passed down from parent to offspring

Question 12

Allele

Answer 12

A different form of a gene, example gene codes for eye colour (blue, green, brown)

Question 13

Multiplication Rule

Answer 13

If the occurrence of one event does not affect the probability of another event then the probability of their joint occurrence is the product of their independent probabilities. (Often when gender is specified)

Question 14

Test cross

Answer 14

If an individual has the recessive trait, we know what his genotype is aa, if an individual has the dominant trait we cannot be certain what his genotype is, AA or Aa. To perform a test cross you mate the individual in question with an individual who is homozygous recessive, an examination of the offspring will tell you the genotype of the individual in question

Question 15

Incomplete Dominance

Answer 15

Occurs when neither of the two alleles are dominant over the other, the traits blend together. A heterozygote would have a trait that is intermediate between the paternal traits. Example red and white parent flowers produce pink flowers.

Question 16

Co-dominance

Answer 16

Occurs when both of the alleles are expressed, both are dominant. Example: RR and WW, F2 generation displays a 1:2:1 ratio

Question 17

Multiple Alleles

Answer 17

Occurs when more than 2 alleles determine the individuals phenotype. No set number of alleles that can control a trait, called allelic series
Example: ABO blood typing in humans

Question 18

ABO Bloodtyping

Answer 18

The A allele (I^A) and B allele (I^B) are codominant and both are dominant to the O allele (i)

Question 19

Monohybrid Crosses

Answer 19

Considers the inheritance of one trait

Question 20

Dihybrid Crosses

Answer 20

Considers the inheritance of two traits

Question 21

Independent Assortment

Answer 21

Genes for 2 traits can go together in different combinations, due to the different ways that the chromosomes can line up during meiosis 1 when gametes are being made.
Example: GgYy could pass on GY, Gy, gY, gy

Question 22

Polygenic Inheritance

Answer 22

Continuos traits are controlled by

More than just one gene. A group of genes that all contribute to the same trait are called polygene

Question 23

Continuous Traits

Answer 23

Some traits do not appear as one form or another but as a whole range of possibilities
Example: Human Height

Question 24

Independent assortment of genes on the same chromosome

Answer 24

Genes that are located on the same chromosome do not assort independently, the genes will be passed on together because it is the chromosomes that are distributed in the gametes.

Question 25

Linked Genes

Answer 25

Genes on the same chromosome

Question 26

Chromosomal Theory of Inheritance

Answer 26

States that genes are located on chromosomes and chromosomes are passed on to offspring. If 2 genes are located on the same chromosome then they will be passed on together to the offspring

Question 27

Sex linked traits

Answer 27

Genes located on a sex chromosome

Question 28

Examples of sex linked traits

Answer 28

Hemophilia, red-green color blindness, duchenne’s muscular disorder

Question 29

Discovery of sex linkage and result

Answer 29

Discovered a white eyed male when the wild type eye color is red. Concluded that the gene for eye color is located on the X chromosome, there is no corresponding eye color site on the Y chromosome. Since the mutant allele is recessive a female must receive two copies of this gene for this trait while males only have to receive one copy for this trait.

Question 30

Characteristics of Sex Linkage

Answer 30

More males than females show the recessive phenotype, no father to son transmission but all daughters are carriers, one half of sons from carrier mothers will be affected

Question 31

Colour Blindness

Answer 31

Red-green color blindness is X linked

Question 32

Barr Bodies

Answer 32

The non-functioning X chromosome in a female, each cell in a females body only has 1 functioning X chromosome. Which chromosome is inactivated is random in every cell

Question 33

Crossing over Mechanism

Answer 33

Crossing over occurs during prophase 1, and it occurs between homologous chromosomes at Chiasmata. The farther apart two linked genes are the greater probability for crossing over.

Question 34

Gene Mapping

Answer 34

The percentage of crossing over can be used to map the distance between linked genes on a chromosome, each crossing over percentage=one map unit

Question 35

Crossing over Frequency

Answer 35

Proportional to the distance that separates genes

Question 36

Calculating Map Distance (map units or crossing over frequency)

Answer 36

Map distance= number of recombinant types/ total number x100

Question 37

Pedigree Analysis

Answer 37

First thing you must do is determine the mode of inheritance, sex linked or autosomal. If autosomal is it dominant or recessive, then fill in the genotype a of the individuals

Question 38

Sex linked pedigree analysis

Answer 38

There is significantly more affected males than females, if there is close to the same number of males and females it is autosomal. Mode of transmission is generally from the mothers side to her sons.

Question 39

Dominant vs recessive

Answer 39

For dominant traits you need only one of the traits alleles to express that trait (AA or Aa). For recessive traits you need both of the traits alleles to express that trait (bb)

Question 40

Recessive pedigree analysis

Answer 40

If the traits skips a generation it is likely a recessive trait
Example: two people without the trait have a child with the trait, this could not happen if the trait was dominant

Question 41

Dominant

Answer 41

An easy way to tell if a trait is dominant is that at least one affected individual will be doing in every generation. In a pedigree if every affected individual has at least 1 parent who is also affected you can assume the condition is dominant.
Example: two people with the trait have a child who does not have the trait- means it is dominant